1. Field of the Invention
This invention relates to a network of asynchronous speed-independent nodes and more particularly to such a network wherein each node is made up of a five port module of arbiter and selector switches.
2. Description of the Prior Art
Asynchronous speed independent circuits or networks are such that arbitrary delays have no effect upon the circuit operation. An arbiter switch is a switch or node that receives an asynchronous transmission from one of two different input ports and transfers that message in an asynchronous manner to its output port. Such an arbiter switch is disclosed in the Clark U.S. Pat. No. 4,251,879, and also in the Bolton et al U.S. patent application, Ser. No. 329,424, filed Dec. 10, 1981, both of which are assigned to the assignee of the present invention.
A selector switch is a switch which receives a message on its input port and transmits it to one of two output ports according to the first bit in the serial transmission to be received. Such a selector switch is disclosed in the Clark U.S. Pat. No. 4,237,447 and also in the Bolton et al U.S. application, Ser. No. 329,423, filed Dec. 10, 1981, both of which are assigned to the assignee of the present invention. By employing these two switches, various networks can be created in a variety of configurations such as described in the Barton et al U.S. Pat. No. 4,307,446 and also in the Hagenmaier et al U.S. patent application, Ser. No. 281,065, filed July 7, 1981, both of which are assigned to the assignee of the present invention.
In networks such as the type referenced above, a node, desiring to transmit a message to another node, begins its transmission which establishes a path between the respective nodes, which path becomes dedicated to that transmission until an end-of-message signal is received by the destination, and an acknowledge of end-of-message signal is transmitted back through the various switches of the path to the source. In the above-described Barton and Clark patents, such a dedicated path caused delays in freeing the network for the establishment of different transmission paths due to the time it takes for the end-of-message signal to reach the destination and the acknowledge end-of-message signal to be transmitted back to the source. Furthermore, if a particular switch in the established path failed to respond to an end-of-message signal or its corresponding acknowledgment signal, transmission by other nodes could be blocked indefinitely. The switches of the such that any node could unblock a transmission path to its desired destination should that path be blocked for an unduly long period of time.
The above-referenced Hagenmaier application is directed toward a particular network of concurrent processors which are adapted primarily for nearest neighbor communication. In this network, each processor storage module is connected to the network grid by a port formed of three nodes where each node is a hexagonal circuit formed of three selector switches and three arbiter switches. Each such node at most could handle three dedicated message paths and, more often than not, only one. After a few paths have been established between different processors, it becomes increasingly difficult for other sources in the network to establish a transmission path to one of their destinations.
The provision of a clear signal for the switches of the above-described Bolton et al applications freed the available transmission paths to a certain extent. However, any particular port could still handle only a couple of simultaneous transmission paths.
It is, then, an object of the present invention to provide a port for an asynchronous network of concurrent processors that can accommodate a number of different transmission paths.
It is another object of the present invention to provide an asynchronous network port having a number of transmission paths that are not continuously dedicated to the duration of the transmission of a particular message along the path.
It is still a further object of the present invention to provide an asynchronous network port having a number of transmission paths which may be cleared or reset when it is determined that particular paths in the network are not operating properly.